BUG report

Here is a bug with multiple files project. Show up when creating new nodes. 

>>>>>>>>>>>>>>>>> in low_level.c
>>>>>>>>>>>>>>>>> pb with more than a file in the project
>>>>>>>>>>>>>>>>> because of a global var not updated "idfirst"

FIX done:

---> moved at the beginning of the file 
static idfirst = 1; /* used for redoing the ids of nodes */

----> addition in routine int Init_Tool_Box()
  if (cur_proj)
      for (ptb = PROJ_FILE_CHAIN (cur_proj); ptb ; ptb =  BLOB_NEXT (ptb))
added --> idfirst = 1;
	  pointer_on_file_proj = (PTR_FILE) BLOB_VALUE (ptb);